1. Field of the Invention
The present invention relates to a vehicle bearing assembly to which a wheel is attached.
2. Description of the Related Art
To detect the speed of a vehicle or actuate an antilock brake system (ABS), a rotational speed detection sensor is attached to a vehicle bearing assembly to which a wheel is attached and the rotational speed of the axle (wheel) is detected. The vehicle bearing assembly has: an inner ring member, which is a rotary member that constitutes a flanged axle; an outer ring member, which is a stationary member fixed to the vehicle body via a steering knuckle; two rows of rolling elements disposed between the inner ring member and the outer ring member; cages that retain the rolling elements, and so on. A detection object, such as a pulser ring, is attached to the inner ring member that rotates together with the wheel, and a rotational speed sensor, which detects the rotational speed of the detection object, is attached to the outer ring member as a non-rotating side. The rotational speed sensor is inserted into a sensor mounting hole extending through a cover provided at the end of the outer ring member. The cover is placed over the inboard side of the outer ring member. An O-ring is provided between an outer peripheral surface of the rotational speed sensor and an inner peripheral surface of the sensor mounting hole. The O-ring is fitted in a circumferential groove formed in the outer peripheral surface of the rotational speed sensor, and seals the gap between the rotational speed sensor and the sensor mounting hole. The O-ring prevents the entrance of contaminants into the inside of the roll bearing through the gap between the rotational speed sensor and the sensor mounting hole (see Japanese Patent Application Publication No. 2004-52833)).
To provide an O-ring between the rotational speed sensor and the sensor mounting hole, the rotational speed sensor is inserted into the sensor mounting hole with the O-ring fitted in the circumferential groove in the outer peripheral surface of the rotational speed sensor. Because the outer diameter of the O-ring before the O-ring is compressively deformed is greater than the inner diameter of the sensor mounting hole, the rotational speed sensor cannot be inserted without compressively deforming the O-ring, and a specific force (a force in the axial direction required to insert the rotational speed sensor into the sensor mounting hole, which may be hereinafter referred also as “insertion force”) is necessary to insert the rotational speed sensor. When a large insertion force is required, the efficiency in assembling the vehicle bearing assembly decreases.
When the O-ring abuts against the edge of the opening on the sensor insertion side, the surface pressure on the O-ring increases and the insertion force tends to be excessively large. Thus, it is considered desirable to provide a uniform (conically tapered) chamfered portion 61 along the entire edge of the opening of the sensor mounting hole 60 on the outer face of the cover (sensor insertion side) as shown in FIG. 5 to reduce the required insertion force.
It has, however, been found that the required insertion force cannot be reduced sufficiently even if the chamfered portion 61 is provided as described above. That is, it has been found that the insertion force becomes excessively large when the O-ring is moved through the chamfer edge portion 63 (see FIG. 5) as the boundary between the inner peripheral surface 62 of the sensor mounting hole 60 and the chamfered portion 61 in that case. Because the O-ring undergoes especially significant compression deformation when the O-ring is moved through the chamfer edge portion 63, at which the diameter of the chamfered portion 61 is smallest, and because the surface pressure on the O-ring may become excessively large because of the edge shape of the chamfer edge portion 63, a large insertion force is required.